Electromagnetic apparatus



Sept. 13, 1932. E. FALKENTHAL ELECTROMAGNETIC APPARATUS Filed Jan. 29, 1931 IHVEHTO fran' n Falkenfh al HTTOHEY Patented Sept. 13, 1932 UNITED` STATES PATENT OFFICE n ERWIN FALKENTHAL, OF IBERLIN-DAHLEM, GERMANY, ASSIGNOR OF FIFTY PEB CENT TO RADIO PATENTS CORPORATION, F NEW YORK, N. Y., A CORPORATION' OI l NEW yYom:

ELECTROMAGNETIC APPARATUS Application led January 29, 1931, Serial No. 512,009, and in Germany February 19, 1980.

My invention relates to magnetic or electromagnetic apparatus and more particularly .to iron cores servlng as conductors Vfor the able period of time.

tion, in conjunction with the accompanymg drawing, which I have chosen for illustrating more clearly the novel features of the invention. f

Figures 1 and 2 illustrate in a schematicl manner a front and side view of a transcommon to use an alloy of iron and silicium ornickel, or any other suitable alloy, in place of pure-iron. Such iron sheets commonly used in construction of electrical machines and signalling apparatus have, in most cases, a very thick oxide surface due to the particular treatment duringA the manufacturing process, especially when the sheets have been annealed, or furthermore when they have been stored during long periods of time. This has the effect that the effective cross section of the magnetic cores composed of such sheets is considerably decreased, naturally entailing further losses as to the magneti-c action.

It has already been suggested to obviate these disadvantages by galvanizing the iron or alloy sheets. This method, however, could not be used satisfactorily as yet, probably in view of the increased time and expense required for the necessary preliminary treatment of the sheets for such a` process. This preliminary treatment has to be carried out very carefully, as otherwise no permanent and effective deposits on the sheets could be secured.

If, furthermore, it is desired to minimize or practically eliminate losses due to circulating or eddy currents inthe iron core produced by variation of thek magnetic flux passing through it, it is necessary to apply the sheets with a coating of an insulating material, such as lacquer or paper, as is usually used in practice. This latter method causes a considerable increase in the cost of the sheets, as will be obvious and in this case the effective iron cross section also receives a considerable decrease, on account of the` space required 1 for the lacquer or paper insulation.

The afore-mentioned disadvantages are overcome by the resent invention hereinafter described andJ consisting in theuse of iron or suitable alloy sheets-iron silicium or iron nickel alloys, etaprovided with a very thin surface coating of aluminum.

This coating may be applied preferably according to a well-known process by rolling on to the iron sheet thin aluminum foll at norma-l or cold temperature and under a very high pressure. Through such an aluminum coating the surface oxidation of the iron sheets,

is prevented even after very extended storing periods, whereb an increase of the electric and magnetic e ciency of the apparatus comprising such sheets is obtained.

.Theafore-mentioned process presents the further advantage that the hystereses losses in view of the additional surface coating of the iron sheets is still further decreased to some extent. The cost of the aluminum coatthousandths of a millimeter is fairly small when applied simultaneously during the rolling process of the sheets; that is, during one and the same production process. .In such cases where it Iis desired to decrease the edd current losses,thealuminumcoatinginaccor ance with a further feature of the invention is furthermore provided with an oxide surface by surface oxidation in that, for instance, the sheets after leaving'the rolling mills are passed through a suitable solution,

mature cores of electric machines, magnetic cores for signaling apparatus, such as of telephones, loud speakers and, in general, in

w all such cases where iron cores composed of individual sheets are required.

Referring to the drawing, I have illustrated in a schematic manner a transformer as used for electrical purposes, comprising a core C consisting of individual iron punchings z' or punchings of a suitable iron alloy stacked upon each other as shown by Figure 2. The core carries a winding w, which is well knownin the art.

wound on a suitable su port, in a manner 'he winding w ma consist of a primar and secondary win ing, or it may be a slngle winding, as in the case of an auto-transformer or of a choke coil son to the iron core base z'.

andthe like. serving as a conductor of the magnetic lines of force or the magnetic flux, as indicated by the dotted line f. This flux may be a unidirectional flux varying in intensity, or may be an alternatin flux periodically changin itsv direction an in both cases it is desired to 'prevent the nerationof circulating or eddy currents, gdr which urpose the core consists of sheets z' separate Yfrom each other by 'the non-conducting oxide surface of the aluminum coating applied to the sheets z', as seen from Fi re 2, or more clearly from Figure 3. In igure 2 the dimensions of the aluminum coating and its oxide surface o are unproportionately exaggerated in com ari- Figure 3 s ows approximately the real proportions in an enlarged manner.

Although I have described my invention with specific reference to the disclosure and the showin of the drawing, it is understood that modi cations and variations are possible in accordance with its general aspects and broad scope, as expressed in the appended claims.

What I claim is 1. In an iron core for electrical a paratus composed of iron sheets provided with minum coating.

2. In a magnetic core for electrical ap aratus, being composed of single sheets staclged upon each other, in which iron sheets are used provided with a thin aluminum coating.

3. In a magnetic core for electrical apparatus, being composed of single sheets stacked upon each other, in which said'sheets consist substantially of magnetic material with a thin aluminum coating, the outside surface of said aluminum coating, in turn, being provided with a second aluminum oxide coating.

4. In a magnetic core for electric apparatus, being composed of single sheets stacked upon each other, in which said sheets consist substantially of an iron base provided with a thin aluminum coating, the outside surface of said aluminum coating consisting of aluminum oxide.

5. In a magnetic core for electrical apparatus, com rlsing iron sheets of magnetic base material, the method of manufacturing said iron sheets which consists in rolling on under pressure a thin aluminum foil to the magnetic base material and subsequently passing the sheet through an oxidizing agent.

6. In a magnetic core for electrical apparatus, comprising aluminum coated sheets, the method of manufacturing said aluminum coated sheets, which consists in rolling on under ressure a thin aluminum foil to the iron s eets and subsequently passing the sheets througha bath of acetic acid for producing an aluminum oxide surface.

In testimony whereof I a'fx my si ature.

ERWIN FALKENT AL.

The core C has the object of analu- 

